"An assessment by a specialist registrar psychiatrist could have produced a differential diagnosis of paranoid schizophrenia then Rakeim could have been removed from his grandmother's home, the outcome of which is that she would not have been unlawfully killed by stab wounds of the head and neck."

He continued: "Rakeim Regan was a dependent person who was seriously mentally ill with a psychotic illness.

"The failure by those involved to have him assessed by a specialist registrar psychiatrist... provides the causal connection with the events which led to the death of Patricia Ann Regan."

Policy changed

In a statement released after the inquest, Mrs Regan's family said: "It has taken four years but finally we have got to the truth of how Pat and Rakeim were let down and failed by Leeds mental health crisis team."

Chris Butler, the chief executive of Leeds and York Partnership NHS Foundation Trust, said: "The assessment of Rakeim Regan in 2008 was carried out with the best of intentions by a single practitioner in order to provide a rapid response to an urgent situation.

"We fully accept the coroner's findings regarding the absence of on-call specialist doctors during the trust's interaction with Rakeim Regan.

"We are committed to continually improving our services and we have already changed our policy and procedures following a review undertaken immediately after the incident."

Mrs Regan's anti-gun campaign started after her son Danny, 25, was shot dead in 2002.

She had been a high-profile campaigner and met government officials to discuss how to tackle the problems of guns and gang-related crime.